Conventionally, there has been used a spark plug in which noble metal tips are provided on ends of respective electrodes. A method of manufacturing such a spark plug usually employs a step of forming a composite tip by joining a noble metal tip and an intermediate tip (e.g., an Ni tip) together, and joining the intermediate tip of the composite tip to an end of an electrode.
However, since the noble metal tip and the intermediate tip are such small members that their diameters and heights are about 1 mm, in formation of a composite tip by laser-welding them together, it is not necessarily easy to properly align the height of radiation of a laser beam with the height of the boundary between the two tips. Notably, such a problem is not a problem which occurs only in a process of joining a noble metal tip and an intermediate tip together, but is a common problem which occurs in general cases where two tips are joined together.